Conventionally, there has been proposed a lighting device including a power supply unit to adjust a color and a quantity of illumination light by adjusting the light quantity of each of a plurality of light emitting elements with different emission colors according to a dimming signal inputted from a controller (see, e.g., Japanese Unexamined Patent Application Publication No. 2013-168382).
The power supply unit described in Japanese Unexamined Patent Application Publication No. 2013-168382 is connected to an AC power source and supplied with a power through two wires. Further, the power supply unit is connected to the controller through two other wires. The controller outputs a control signal to the power supply unit in response to the operation of an operating unit provided rotatably. According to the control signal inputted from the controller, the power supply unit controls the light quantity of the respective light emitting elements to adjust the color and the quantity of the output light.
In the lighting device described in Japanese Unexamined Patent Application Publication No. 2013-168382, a total of four wires including the two wires for connection to the AC power source and the two wires for connection to the controller are connected to the power supply unit.
Meanwhile, in the existing houses or facilities, in a case where a phase control type dimmer is installed to dim an incandescent lamp, the dimmer and the incandescent lamp are connected to each other through two wires. If the above-mentioned lighting device and light emitting diodes are used instead of the dimmer and the incandescent lamp, it is necessary to install two wires for the dimming signal in addition to the two wires for connecting the phase control type dimmer to the incandescent lamp. If it is intended to install additional wires in the existing houses or facilities, it is necessary to pass the wires through the back side of the wall, and it may take time and effort to perform the wiring work.